If you are experiencing frequent delays and slowness on your Internet, most likely that you would blame it on your Internet Service Provider (ISP). But the problem can also be on your side. For example, if you have a virus/trojan/spyware/etc, they can use up your bandwidth causing overall degradation in your Internet performance.
Beside keeping your system clean, you should also consider prioritizing your Internet connections. Read up on your router's documentation on how to configure and prioritize ports. Term used such as QoS (Quality of Service) can enhance your Internet experience by prioritizing ports that you consider more important.
Some of the most important ports are:
Ports tcp80, tcp443 for browsing Internet
Ports tcp25, tcp110, tcp143, tcp587 for emails
If you are a gamer Port Forward provides various ports numbers for the matching games.
Good luck, and remember, keep your computer(s) free of malwares and your router tuned. It will not only enhance your Internet experience, but will help reduce congesting Internet, reduce support costs which may reduce your future fees, and reduce frustrations.